U.S. patent number 5,885,738 [Application Number 08/847,546] was granted by the patent office on 1999-03-23 for method for making and using an improved durable printable sheet.
This patent grant is currently assigned to W. L. Gore & Associates, Inc.. Invention is credited to Gregory E. Hannon.
United States Patent |
5,885,738 |
Hannon |
March 23, 1999 |
Method for making and using an improved durable printable sheet
Abstract
The present invention is an improved printable sheet for use in
a variety of applications requiring extreme image durability and
weather (e.g., water) resistance. The printable sheet of the
present invention employs an expanded polytetrafluoroethylene sheet
comprising a series of polymeric nodes interconnected by fibrils.
Images can be applied to this sheet using a variety of means,
including pen and ink, electrostatic printing, screen printing,
offset printing, etc. These images have proven to be very durable
and capable of substantial wear, water exposure, and general abuse.
Moreover, the printable sheet of the present invention is capable
of being cleaned and reused over and over again once any given
image is no longer of interest.
Inventors: |
Hannon; Gregory E. (Newark,
DE) |
Assignee: |
W. L. Gore & Associates,
Inc. (Newark, DE)
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Family
ID: |
23472040 |
Appl.
No.: |
08/847,546 |
Filed: |
April 23, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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419343 |
Apr 10, 1995 |
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373350 |
Jan 17, 1995 |
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Current U.S.
Class: |
430/124.15;
430/124.51; 430/124.53; 101/483; 134/40; 134/38; 427/261; 427/282;
427/407.1 |
Current CPC
Class: |
G03G
7/008 (20130101); B41M 5/529 (20130101); B41M
1/30 (20130101); B41M 3/00 (20130101); G03G
7/0093 (20130101); G03G 7/004 (20130101); B41M
1/12 (20130101) |
Current International
Class: |
B41M
5/52 (20060101); B41M 5/00 (20060101); B41M
5/50 (20060101); B41M 1/26 (20060101); B41M
1/12 (20060101); B41M 1/30 (20060101); G03G
007/00 (); B05D 001/32 (); B05D 005/00 () |
Field of
Search: |
;430/120,97
;427/282,261,407.1,181,197,352 ;134/38,40 ;101/483 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rodee; Christopher D.
Attorney, Agent or Firm: Lewis White; Carol A.
Parent Case Text
RELATED APPLICATIONS
This application is a continuation, of application Ser. No.
08/419,343 filed Apr. 10, 1995, abandoned which is a divisional of
U.S. patent application Ser. No. 08/373,350 filed Jan. 17, 1995,
abandoned.
Claims
The invention claimed is:
1. A method for producing a reusable durable surface for displaying
a printed image that comprises
providing an image layer comprising an expanded
polytetrafluoroethylene (PTFE) having at least one print surface
comprising a structure of polymeric nodes interconnected by
polymeric fibrils;
applying to the image layer a first printed image formed from a
durable print medium to form a durable bond between the print
surface and the print medium, whereby the printed image adheres to
the polymeric nodes and fibrils while maintaining the node and
fibril structure of the image layer;
whereby the printed image remains clearly adhered to the image
layer so as to provide a clear printed image that will withstand
repeated exposures to water;
changing the printed image on the print surface through the steps
of:
cleaning the surface with a solvent that will remove the printed
image without damaging the image layer; and
applying to the image layer a second printed image formed from a
durable print medium to form a durable bond between the print
surface and the print medium,
whereby the first printed image is applied to the image layer
through a xerographic printing process.
2. The method of claim 1 that further comprises
reinforcing the image layer by adhering it to a dimensionally
stable support layer.
3. The method of claim 1 that further comprises
creating a printed image that will withstand at least 5 hours of
continuous clothes washing machine washings;
whereby the printed image remains clear following the machine
washings.
4. The method of claim 1 that further comprises
providing a printed image on the image layer to form a map;
whereby the map is both packable and waterproof.
5. The method of claim 1, wherein both said first printed image and
said second printed image are applied to the image layer through a
xerographic process.
6. A method for producing a reusable durable surface for displaying
a printed image that comprises
providing an image layer comprising an expanded
polytetrafluoroethylene (PTFE) having at least one print surface
comprising a structure of polymeric nodes interconnected by
polymeric fibrils;
applying to the image layer a first printed image formed from a
durable print medium to form a durable bond between the print
surface and the print medium, whereby the printed image adheres to
the polymeric nodes and fibrils while maintaining the node and
fibril structure of the image layer;
whereby the printed image remains clearly adhered to the image
layer so as to provide a clear printed image that will withstand
repeated exposures to water;
changing the printed image on the print surface through the steps
of:
cleaning the surface with a solvent that will remove the printed
image without damaging the image layer; and
applying to the image layer a second printed image formed from a
durable print medium to form a durable bond between the print
surface and the print medium,
whereby the first printed image is applied to the image layer
through a screen printing process.
7. The method of claim 6 that further comprises
creating a printed image that will withstand at least 80 hours of
continuous clothes washing machine washings;
whereby the printed image remains clear following the machine
washings.
8. The method of claim 6, that further comprises reinforcing the
image layer by adhering it to a dimensionally stable support
layer.
9. The method of claim 6, wherein both said first printed image and
said second printed image are applied to the image layer through a
screen printing process.
10. A method for producing a reusable durable surface for
displaying a printed image that comprises
providing an image layer comprising an expanded
polytetrafluoroethylene (PTFE) having at least one print surface
comprising a structure of polymeric nodes interconnected by
polymeric fibrils;
applying to the image layer a first printed image formed from a
durable print medium to form a durable bond between the print
surface and the print medium, whereby the printed image adheres to
the polymeric nodes and fibrils while maintaining the node and
fibril structure of the image layer;
whereby the printed image remains clearly adhered to the image
layer so as to provide a clear printed image that will withstand
repeated exposures to water;
changing the printed image on the print surface through the steps
of:
cleaning the surface with a solvent that will remove the printed
image without damaging the image layer; and
applying to the image layer a second printed image formed from a
durable print medium to form a durable bond between the print
surface and the print medium,
whereby the first printed image is applied to the image layer
through an offset printing process.
11. The method of claim 10 that further comprises
creating a printed image that will withstand at least 100 hours of
continuous clothes washing machine washings;
whereby the printed image remains clear following the machine
washings.
12. The method of claim 10, that further comprises reinforcing the
image layer by adhering it to a dimensionally stable support
layer.
13. The method of claim 10, wherein both said first printed image
and said second printed image are applied to the image layer
through an offset printing process.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to durable substrates for displaying
printed images (e.g., images produced by lithography,
photolithography (e.g., xerographic copying), screen printing,
gravure printing, offset printing, etc.), and methods for producing
and using such substrates.
2. Description of Related Art
There has been a demand over the years for a durable substrate for
use as a printable sheet. Whether for use with hand writing
instruments, offset printing, xerographic printing processes (e.g.,
photocopiers, laser printers, or fax machines), screen printing,
etc., there are many applications where a flexible, weatherproof
material is desirable. For example, maps and other charts for
outdoor use (e.g., ship charts, road and backpacking maps,
schematic drawings for outdoor workers, etc.) are often exposed to
extreme weather conditions and are regularly abused during use,
such as by crumpling, improper folding, or being soiled with food,
drink or dirt. Extreme environments have even more taxing demands,
such as that encountered by charts or other documents used
underwater.
A number of materials have been proposed to address some of these
demands. For instance, a wide variety of coating materials have
been proposed for use on conventional paper materials. Examples of
such coatings are disclosed in U.S. Pat. No. 4,966,804 to Hasengawa
et al., and 5,0313,621 to Kistner. While these materials may work
adequately well for some applications, they all have undesirable
limitations. Materials that are coated after application of the
printed image are not readily amenable to a durable correction or
modification after treatment. A more pressing concern is that
coated paper products have only limited ability to withstand
exposure to water or other weathering conditions. Breakdown under
these conditions is even more pronounced when the materials are
subjected to repeated folding or crumpling that may weaken or
destroy the protective coating.
A number of other materials are employed that are fully weather
resistant. One example of such material is described in U.S. Pat.
No. 3,871,947 to Brekken. This material is a polymer film of
polyethylene terephthalate, such as that used as an adhesive tape.
While this material is far more weather resistant than coated paper
materials, it tends to provide only a weak adhesion to most print
media. As a result, most printed images will not remain on this
type of material when subjected to active use or weathering.
Another problem with plastic materials of this type is their
expense both in production and printing. Although plastic materials
are far more durable in use, they are generally incapable of reuse
(i.e., permanent inks that must be used on these materials are not
generally capable of removal) and these materials may present
serious disposal concerns.
One common material used for applications where a permanent,
weatherproof printed material is needed is spun bonded nonwoven
high density polyethylene material sold under the trademark TYVEK
by E. I. duPont de Nemours and Company, Inc. This material is
highly tear-resistant and will withstand extensive exposure to
water or other weathering conditions. As a result, images are often
applied to this material where durability and weather-resistance is
needed (e.g., backpacking maps and similar applications where the
material may get wet or soiled). Despite improvements in
durability, repeated exposure to water, and particularly the rigors
of machine washing, demonstrates that the images on TYVEK maps will
readily fade and the material will lose its shape. Accordingly,
this material can be considered only moderately durable and not
suitable for repeated exposure to extreme conditions. TYVEK
material also continues to suffer from the problems of other
plastic materials outlined above, such as compatibility with only
certain print materials, inability to be readily cleaned and
reused, and possible disposal problems following use.
Although it would be desirable to provide a print substrate that
will accept and retain a wide variety of print images through
severe water exposure and other extreme conditions, until the
present invention no such material has been available. Of
particular interest would be a print substrate that can retain
images produced by a xerographic print process (e.g., from
photocopiers or laser printers) through repeated exposure to water
and abuse through robust use. Of even greater interest would be a
material that can both successfully retain an image during use and
also be readily cleaned and reused repeatedly as desired.
These and other purposes of the present invention will become
evident from review of the following specification.
SUMMARY OF THE INVENTION
The present invention is an improved printable sheet for use in
displaying a variety of printed images and method for using such a
sheet. The printable sheet of the present invention comprises an
image layer of expanded polytetrafluoroethylene (PTFE) comprising a
surface of polymeric nodes interconnected by fibrils. Preferably,
this image layer is attached to a dimensionally stable support
sheet to aid in maintaining the shape of the printable sheet. It
has been determined that a variety of images can be applied to the
image layer, with the printed image attaching to and within this
structure to produce both a clear image and one that is well
protected from attack during use. Thus, images applied in
accordance with the present invention are highly durable and will
withstand substantial wear, weathering (including complete water
submersion), and abuse without serious damage to either the image
or the printable sheet. Among the printing processes that have
proven satisfactory for use with the present invention are
electrostatic copying, screen printing, conventional pen and ink
writing, and offset printing.
A further inventive aspect of the present invention is that the
printable sheet is capable of being cleaned and reprinted. The
printable sheet's durability and chemical resistance allows the
image layer to be cleaned of old images using appropriate solvents
(without damaging the image layer) and then re-printed. As a
result, the printable sheet of the present invention has the unique
ability of being both highly durable and being readily reusable
once the original image is no longer of interest.
The printable sheet of the present invention has endless possible
applications, including serving as an easily printable durable
surface for use under extreme conditions, such as in maps, field
guides, outdoor writing tablets, specifications and other printed
matter for use underwater, blueprints for outdoor construction,
etc.
DESCRIPTION OF THE DRAWINGS
The operation of the present invention should become apparent from
the following description when considered in conjunction with the
accompanying drawings, in which:
FIG. 1 is a plan view scanning electron micrograph (SEM) enlarged
7,000 times of one embodiment of an expanded
polytetrafluoroethylene (PTFE) material for use as an image layer
of the present invention;
FIG. 2 is a three-quarter view SEM enlarged 7,000 times of an
expanded PTFE material of the present invention;
FIG. 3 is a plan view SEM enlarged 7,000 times of an expanded PTFE
image layer of the present invention showing a printed image bonded
thereto;
FIG. 4 is a three-quarter view SEM enlarged 7,000 times of an
expanded PTFE image layer of the present invention showing a
printed image bonded thereto;
FIG. 5 is a three-quarter isometric view of a durable printable
sheet of the present invention, displaying printed images
thereon;
FIG. 6 is a cross-section view of one embodiment of a durable
printable sheet of the present invention, comprising a single layer
of expanded PTFE material;
FIG. 7 is a cross-section view of another embodiment of a durable
printable sheet of the present invention, comprising a layer of
expanded PTFE material bonded to a support layer.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is an improved printable sheet for displaying
a printed image. The term "printed image" is intended to include
any kind of print medium that is used to record an image (e.g.,
words, pictures, drawings, tables, etc.) on a surface. As is
explained in greater detail below, print media contemplated by the
present invention include a variety of inks (e.g., pen ink, screen
print inks, or printer's ink), printer toner and other particulate
materials, xerographic toner, etc.
FIGS. 1 and 2 are scanning electron micrographs (SEM) of image
layers of a printable sheet of the present invention. The image
layer 10 comprises a polymer material that includes a microporous
structure of polymeric nodes 12 interconnected by fibrils 14. As is
explained in greater detail below, preferably the image layer
comprises an expanded polytetrafluoroethylene (PTFE) material, such
as that made in accordance with U.S. Pat. No. 3,953,566 to Gore,
incorporated by reference.
Expanded PTFE has a number of important properties that make it
particularly suitable as a durable print display surface of the
present invention. First, PTFE is a highly inert material that is
hydrophobic. Accordingly, the material is resistant to both water
and a wide variety of other materials that commonly damage paper
and similar printed surfaces. Additionally, by expanding PTFE in
the manner taught by U.S. Pat. No. 3,953,566 to form a node and
fibril structure, the material undergoes a significant increase in
tensile strength and becomes highly flexible. Moreover, while full
density PTFE material tends to be a poor surface for retaining a
printed image, since the material is so slippery and resistant to
adhesion that most ink or other print media will not readily adhere
to it, it has been discovered that the node and fibril structure of
expanded PTFE provides a textured surface that will very
effectively retain certain print media thereon and therein.
The preferred printable sheet of the present invention is made in
the following manner. A fine powder PTFE resin is blended with a
lubricant, such as odorless mineral spirits, until a compound is
formed. The volume of lubricant used should be sufficient to
lubricate primary particles of the PTFE resin so to minimize the
potential of the shearing of the particles prior to extruding.
The compound is then compressed into a billet and extruded, such as
through a ram type extruder, to form a coherent sheet of extrudate.
A reduction ratio of about 30:1 to 300:1 may be used (i.e.,
reduction ratio=cross-sectional area of extrusion cylinder divided
by the cross-sectional area of the extrusion die). For most
applications a reduction ratio of 75:1 to 100:1 is preferred.
The lubricant may then be removed, such as through volatilization,
and the dry coherent extrudate sheet is expanded rapidly in at
least one direction about 1.1 to 50 times its original length (with
about 1.5 to 2.5 times being preferred). Expansion may be
accomplished, such as through the method taught in U.S. Pat. No.
3,953,566, by passing the dry coherent extrudate over a series of
rotating heated rollers or heated plates at a temperature of
between about 100.degree. and 325.degree. C. Alternatively, the
extruded sheet may be expanded in the manner described in U.S. Pat.
No. 4,902,423 to Bacino, prior to removal of the lubricant.
In either case, the material may be further expanded at a ratio of
1:1.1 to 50:1 (with 5:1 to 35:1 being preferred) to form a final
microporous sheet. Preferably the sheet is biaxially expanded so as
to increase its strength in both its longitudinal and transverse
directions. Finally, the material may be subjected to an amorphous
locking step by exposing it to a temperature in excess of
340.degree. C.
The final sheet preferably comprises the following mean properties:
thickness of about 1.6 mils; resistance to air flow (Gurley Number)
of about 6.0 sec.; bubble point of about 21.2 psi; mass/area of
about 17.7 g/m.sup.2 ; matrix tensile strength in the longitudinal
direction of about 7,014 psi and in the transverse direction of
about 14,353 psi; maximum pore size of 0.43 micron; minimum pore
size of 0.27 microns; and mean pore size of 0.34 microns.
The resistance of the membrane to air flow was measured by a Gurley
densometer (in accordance with ASTM Standard D726-58) manufactured
by W. & L. E. Gurley & Sons. The results are reported in
terms of Gurley Number which is the time in seconds for 100 cubic
centimeters of air to pass through 1 square inch of a test sample
at a pressure drop of 4.88 inches of water.
The Bubble Point of porous PTFE was measured using isopropyl
alcohol following ASTM Standard F316-86, incorporated by reference.
The Bubble Point is the pressure of air required to blow the first
continuous bubbles detectable by the their rise through a layer of
isopropyl alcohol covering the expanded PTFE media. This
measurement provides an estimation of maximum pore size.
Tensile strength is determined by the method described in ASTM
D882, incorporated by reference, using an INSTRON tensile strength
tester.
It has been determined that by providing a microporous surface of
polymeric nodes and fibrils, such as that of expanded PTFE, a
printed image can be coated onto and into the node and fibril
structure so as to establish a surprisingly durable bond between
the printed image and the image layer. As is shown in the SEMs of
FIGS. 3 and 4, the printed image 16 is actually interwoven into the
surface of the expanded PTFE where the microporous structure of the
material serves to shield the image from wear or attack during use.
As is shown in FIG. 5, the printable sheet 10 of the present
invention can be formed into any suitable shape and may have
virtually any form of image applied to it, including writing 18,
charts or map lines 20, etc.
The present invention may comprise a single or multiple layers of
expanded PTFE 22, as is shown in FIG. 6, or may comprise a laminate
of expanded PTFE 22 and a backing support material 24, as is shown
in FIG. 7. Since the expanded PTFE membrane alone tends to be
susceptible to stretching and distortion, it is preferred that the
membrane be mounted to a support layer 24, such as through
lamination to a woven or non-woven fabric material, that will help
maintain the shape of the image layer during use. Suitable support
layer materials include paper, woven materials such as nylon
taffeta fabric, non-woven materials such as felt fabrics, and
continuous polymeric sheets such as urethanes.
A suitable support layer may be laminated in place by applying an
adhesive material, such as moisture-cured solvent-free urethane
adhesive, to the expanded PTFE membrane and then applying the
adhesive-coated expanded PTFE membrane to a fabric material (e.g.,
nylon taslite, nylon taffeta). The two materials can then be bonded
to each other under applied pressure, such as by rolling the
material between one or more pairs of nip rollers. With use of a
moisture curable polyurethane adhesive to bond an expanded PTFE
membrane to a woven fabric, such as nylon taffeta, pressure of 100
pound per linear inch are applied to bond the materials together.
The materials are then allowed to moisture cure for a period of
about 48 hours before use.
A durable water repellent (DWR) may then be applied to the support
layer material to provide additional water resistance, if desired.
Suitable materials for a DWR coating for use in the present
invention include fluoroacrylates or fluorinated urethanes.
A variety of images and print media have been applied to the
substrate of the present invention with exceptional durability
results. In its simplest form, the durable print substrate of the
present invention can be written on with ball-point pens or
markers. More surprisingly, the material of the present invention
can be loaded through a conventional xerographic printing machine
(e.g., a plain paper copier, facsimile machine, or laser printer)
to have a particulate toner image applied to the image layer. It
has been discovered that the toner material forms a semi-permanent
bond within the nodes and fibril structure of the expanded PTFE
that will withstand considerable wear and abuse without significant
loss of image quality.
An even more durable image can be applied through the use of a
screen printing process (e.g., silk screen printing). In these
processes a layer of ink (e.g., Pantone 9089 glossy black ink from
Naz-Dar Co., Chicago, Ill.) is applied using pressure rollers
through a screen to the image layer. As is explained below, images
applied in this manner have proven to be extremely durable, far
exceeding any previously available durable print surface
tested.
Other suitable methods of applying a printed image of the present
invention include block printing, offset printing, engraved
printing, gravure printing, continuous web printing, etc.
The printed image made in accordance with the present invention is
particularly durable with regard to weathering and other water
exposure. As will be evident from the following examples, the
printable sheet of the present invention can be washed continuously
in conventional clothes washing machine (without detergent) for
many hours without any serious loss of image quality. With regard
to particular printed images, the printable sheet of the present
invention will withstand at least 5 hours of continuous washing
with a xerographic image; at least 80 hours of continuous washing
with a screen printed image; and over 100 hours of continuous
washing with an offset printed image. These results demonstrate the
durability of both the printable sheet of the present invention and
the printed images created thereon and provides good indication of
the durability of this material under normal robust outdoor
use.
Another important property of the present invention is that the
printed image can be removed without damaging the image layer,
allowing the material to be used repeated. Due to the very inert
nature of PTFE, it can withstand a wide variety of solvent
materials without any significant degradation. As such, an image
may be removed from the surface using a solvent suitable for a
particular print media without damaging the expanded PTFE image
layer. In many instances, the image may be removed with no more
than a simple wiping of the image with a suitable solvent. For
higher volume print surface regeneration or for those print media
that form stronger bonds to the expanded PTFE material, the print
material may be sprayed, soaked, and/or scrubbed with the solvent,
either manually or through mechanized means.
Particular print media and corresponding solvents are set forth
below:
______________________________________ Print Medium Suitable
Solvent ______________________________________ Electrostatic copier
toner Acetone Ball-point pen ink Acetone Screen printing ink (e.g,
Pantone 9089) Acetone Screen printing-vinyl Acetone
______________________________________
The printable sheet of the present invention has many possible
applications, including serving as an easily printable durable
surface for use under extreme conditions (e.g., maps, ship charts,
field guides, outdoor writing tablets, specifications and other
printed matter for use underwater, blueprints, etc.).
The ability of the printable sheet of the present invention to be
folded, crushed, and otherwise "packed" in manners that would
quickly destroy paper and similar material makes the printable
sheet of the present invention particularly suitable for
applications requiring a packable printed surface, such as
backpacking and other outdoor maps, specification sheets and other
documents that may have to be referred to often and repeatedly
re-packed in outdoor settings, such as trail maps for skiing,
etc.
Without intending to limit the scope of the present invention, the
following examples illustrate how the present invention may be made
and used:
EXAMPLE 1
A printable sheet of the present invention was prepared in the
following manner.
A fine powder PTFE resin was combined with an odorless mineral
spirit. The volume of mineral spirits used per gram of fine powder
PTFE resin was 0.275 cc/gm. This mixture is aged below room
temperature to allow for the mineral spirits to become uniformly
distributed within the PTFE fine powder resin. This mixture was
compressed into a billet and extruded at approximately 8300 kPa
through a 0.71 mm gap die attached to a ram type extruder to form a
coherent extrudate. A reduction ratio of 75:1 was used.
The extrudate is then rolled down between two metal rolls which
were heated to between 30.degree.-40.degree. C. The final thickness
after roll down was 0.20 mm. The material was transversely expanded
at a ratio of 3:1 and then the mineral spirits were removed from
the extrudate by heating the mass to 240.degree. C. (i.e., a
temperature where the mineral spirits were highly volatile). The
dried extrudate was transversely expanded at 150.degree. C. at a
ratio of 3.5:1. After expansion, the sheet was amorphously locked
at greater than 340.degree. C. and cooled to room temperature. This
material forms a relatively fine expanded structure such as that
shown in FIG. 2.
This membrane was then laminated to a nylon taffeta fabric material
by applying to one surface a moisture curable adhesive in a
discrete dot pattern by a gravure roll. The fabric and membrane
were then brought together through nip rollers to bond the two
sheets together with a pressure of about 100 pounds per linear
inch. This laminate was then collected on a round core and the
adhesive was allowed to cure for 48 hours. After curing, a water
based solution containing a suitable fluoropolymer(acrylate) was
applied and the web was then heated to a temperature of at least
150.degree. C. for at least 10 seconds.
EXAMPLE 2
A printed image was applied to the printable sheet made in
accordance with Example 1. The material was cut to approximately
8.5.times.11 inch dimensions and passed through a Sharp SF 8800
photocopy machine employing a Sharp PPC Toner SF-880NT1 Black
(comprising styrene-acrylate copolymer, carbon black, organic
ammonium salt, and polypropylene). A map image was applied to the
printable sheet by simply passing the printable sheet through the
photocopy machine in place of conventional copier paper. The
printed image formed in this manner was of good quality. The map
was capable of being repeatedly folded or crushed (or "packed") and
reopened without damage to either the printable sheet or the map
image.
To test the fastness of the printed image to the printable under
weathering conditions, the printable sheet was exposed to a
continuous wash cycle in a conventional clothes washing machine
employing only water at a temperature of between 25.degree. C. (for
the rinse cycle) and 50.degree. C. (for the wash cycle). The
results of this test are summarized below. After 4 hours, the image
appeared in essentially its original condition slightly but the
printable sheet retained essentially its original shape.
By way of comparison, a similar test was conducted on a commercial
map from Wilderness Press, Berkeley, Calif., printed on TYVEK
fabric. This map was subjected to washing and failed. The image
failed to withstand 3 hours of continuous wash. Further, the TYVEK
material tended to lose its shape and dimensions after only a few
wash cycles.
EXAMPLE 3
The reusability of the printable sheet of the present invention was
then tested using the map image made in accordance with Example 2.
Following the washing machine testing, the printed image was
removed from the surface of the printable sheet by applying an
acetone solvent to the surface. The solvent was wiped across the
image layer of the printable sheet absorbed in a porous cellulosic
substrate (i.e., paper towel) material. After two (2) wipes, the
image was completely removed. The solvent was then allowed to
evaporate from the printable sheet. This material was then
re-printed using the same process described in Example 2. The new
printed image appeared identical to the first in quality and
durability.
EXAMPLE 4
A printed image was applied to the printable sheet made in
accordance with Example 1 using a screen printing process. The
material was cut to approximately 14.times.14 inch dimensions and
Pantone 9089 black glossy type of ink acquired from Naz-Dar Co.,
Chicago, Ill. was used. The image was applied in a conventional
"silk-screening" process whereby an imprintable material was
applied as a reverse image to a piece of fine fabric. The Pantone
9089 ink was rolled across the fine fabric to force the ink in the
form of the image through the fabric onto the printable sheet of
the present invention.
The printed image formed in this manner was of good quality. The
material was capable of being repeatedly folded or crushed (or
"packed") and reopened without damage to either the printable sheet
or the image.
To test the fastness of the printed image to the printable sheet,
the printable sheet was exposed to a continuous wash cycle in a
conventional washing machine employing a no detergent and water at
a temperature of between 25.degree. and 50.degree. C. The results
of this test are summarized below.
The printed image appeared in essentially its original form after
100 hours of washing. Also, the sample withstood flexing in a
NEWARK flex tester acquired from W. L. Gore & Associates, Inc,
of Elkton, Md., at room temperature for 320,000 cycles with no
degradation of image.
EXAMPLE 5
A printed image was applied to the printable sheet made in
accordance with Example 1 using an offset printing process. The
material was cut to approximately 17.times.24 inch dimensions. The
printing was done by using conventional black offset printers ink
supplied by Techna-Graphics Inc., Washington, D.C.
The printed image formed in this manner was of good quality. The
material was capable of being repeatedly folded or crushed (or
"packed") and reopened without damage to either the printable sheet
or the image.
To test the fastness of the printed image to the printable sheet,
the printable sheet was exposed to a continuous wash cycle in a
conventional washing machine employing a no detergent and water at
a temperature of between 25.degree. and 50.degree. C. The printed
image was washed for 177 hours with no image fade. A 2-3% shrinkage
appeared in both directions of the sheet after 20 wash-dry
cycles.
While particular embodiments of the present invention have been
illustrated and described herein, the present invention should not
be limited to such illustrations and descriptions. It should be
apparent that changes and modifications may be incorporated and
embodied as part of the present invention within the scope of the
following claims.
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